1. Field of the Invention
The present invention relates to a radiographic apparatus and method for acquiring moving and still images with a radiation detector, which detects radiation that has passed through a subject and converts the detected radiation into a signal charge carrying image information.
2. Description of the Related Art
In the medical field, there have widely been used radiographic image capturing systems that apply radiation to a subject and guide the radiation that has passed through the subject to a radiation detector, which captures radiographic image information of the subject from the radiation. Known forms of radiation detector panels include a conventional radiation film for recording a radiographic image by way of exposure, and a stimulable phosphor panel for storing radiation energy representing radiographic image information in a phosphor, and reproducing the radiographic image information as stimulated light by applying stimulating light to the phosphor. The radiation film with radiographic image information recorded therein is supplied to a developing device to develop the radiographic image information. Alternatively, the stimulable phosphor panel is supplied to a reading device, which reads the radiographic image as a visible image.
During surgeries, contrast-enhanced imaging procedures, or bone fracture treatments, it is necessary to read radiographic image information from a radiation detector immediately after the radiographic image information has been captured for the purpose of quickly and appropriately treating the patient. As a radiation detector which meets such a requirement, there has been developed a radiation detector referred to as a flat panel detector (FPD) having a solid-state detector (also referred to as pixels) for converting radiation directly into an electric signals or converting visible light, which has been converted from radiation by a scintillator, into electric signals.
As disclosed in Japanese Laid-Open Patent Publication No. 2000-292598, a developed radiation detector is used to capture moving images (radioscopic images) and still images (general images) in the medical field. Moving images are used for observation in angiographic apparatus and bone fracture treatments, and still images are used to carry out accurate image diagnosis of body regions in question. There are certain instances in which the need arises to capture still images of a body region in order to carry out accurate observation and diagnosis while moving images are being captured of the body region.
Japanese Laid-Open Patent Publication No. 2000-292598 discloses a radiographic apparatus, which captures a moving image of a subject at successive frame intervals of t1 (t1= 1/30 [sec], for example) while continuously applying X-rays at a low intensity level to the subject. The radiographic apparatus then stops applying X-rays for a given time of t2 (t2=2×t1), and thereafter captures a still image while applying X-rays at an intensity level which is roughly ten times higher than the low intensity level for an extremely short time tshort (tshort<<t1). Then, the radiographic apparatus stops applying X-rays for a given time of t3 (t3=3×t1−tshort), and thereafter captures a moving image at successive frame intervals of t1 while continuously applying X-rays at the low intensity level to the subject.
Japanese Laid-Open Patent Publication No. 2000-292598 states that when the radiographic apparatus is controlled to operate as described above, still images captured after the moving image has been captured do not contain a ghost of the moving image, and the moving image, which is captured after the still image has been captured, does not contain a ghost of the still image.
When a still image is captured between moving images, it is necessary to define a storage time during which X-rays are stored in pixels of a radiation detector, and a readout time during which the stored X-rays are read from the pixels while the moving images are captured. It also is necessary to define a storage time during which X-rays are stored in the pixels, and a readout time during which the stored X-rays are read from the pixels while the still image is captured. However, such storage and readout times are not defined in Japanese Laid-Open Patent Publication No. 2000-292598.